JPS6121106A - Method and apparatus for forming organic thin film - Google Patents

Abstract

PURPOSE:To obtain an organic thin film free from pinholes and having excellent adhesivity to the substrate, in high efficiency, by melting an organic substance used as a raw material of the thin film, introducing the substance in a molecular form together with other raw material substances into a plasma, and depositing an organic thin film containing the above substances to a substrate. CONSTITUTION:The substrate 2 to be coated is placed on the high-frequency glow discharge electrode 3 furnished with a heater 4, and an earth electrode 1 is placed opposite to the electrode 3. High electrical potential generated by the high-frequency source 6 is applied to the electrodes 1, 3 to generate a plasma. An organic substance used as a raw material for forming a thin film is molten, and is converted to a molecular form taking advantage of the attracting force of an electrical field generated by high potential applied between the discharge electrode and the counter electrode. The molecular substance is introduced into the plasma by the deflector 5 if necessary together with other raw materials. An organic thin film containing the raw material substance and optionally other substances can be deposited on the substrate 2.

Description

Detailed Description of the Invention "Industrial Field of Application" The present invention is directed to substrates made of metals, ceramics, non-porous materials, non-porous materials, etc., which have desired characteristics and excellent adhesion to the substrate. The present invention relates to a method and apparatus for forming organic thin films.

[Prior Art] In recent years, methods have been used to create thin films of organic substances using plasma generated by low-pressure glow discharge.

Typical methods include plasma polymerization and plasma initiated polymerization.

Plasma polymerization is carried out in an atmosphere containing vapors of organic compounds.
Glow discharge is controlled so that low-molecular substances are excited but polymerization products are not easily decomposed, and a thin film of polymeric material is formed on a substrate inserted in or near the plasma. Usually, a high frequency power source is used, and the pressure during discharge is usually 0.1 to 10 Torr.
That's about it.

Since this reaction is carried out in the gas phase, the raw organic substance is usually supplied as a monomer or a low molecular weight gas close to the monomer. The polymerization reaction in plasma polymerization is quite complex, and the structure of the resulting polymer material is often very different from that obtained in normal polymerization reactions. Plasma polymerization has the advantage of simple equipment and easy formation of organic thin films. However, it has the disadvantage that it is difficult to control the reaction and that it is difficult to form a polymer substance with a regular molecular structure.

On the other hand, plasma-initiated polymerization uses plasma as an energy source to start the polymerization reaction.
Unlike the plasma polymerization mentioned above, the reaction mostly proceeds in the liquid phase or solid phase. In plasma-initiated polymerization, the polymerization reaction proceeds in the same way as a normal radical reaction, so the resulting polymer material has regularity. To initiate polymerization, radiation or the like can be used instead of plasma.

However, plasma-initiated polymerization has the disadvantage that the range of applicable compounds is limited (mainly only vinyl compounds) and the reaction rate is slow, so it is only an efficient method for forming thin films.

In addition to these, as a thin film forming method, there is a method in which a solution of a polymeric substance is applied and then the solvent is dried and removed. This is a simple method that has been used for a long time, but it has the disadvantage that it is difficult to improve the adhesion to the substrate.

Furthermore, the thermoplastic resin is melted with high voltage arc sparks,
There is a thermal spraying method that sprays onto the substrate to form a coating layer.
It has the disadvantage that it tends to contain pinholes during film formation, making it difficult to form a dense film.

[Object of the Invention] An object of the present invention is to improve the drawbacks of the conventional organic thin film forming method as described above and to provide a method and apparatus for obtaining a good organic thin film.

[Structure 1 of the Invention] The first gist of the present invention is to melt an organic substance that is a raw material for forming a thin film, make it into molecules, introduce it into a plasma together with other raw materials as desired, and combine the raw material and other raw materials as desired. The present invention relates to a method for forming an organic thin film, which comprises forming an organic thin film containing a raw material on a substrate.

If a monomer gas is introduced directly into the plasma, a complex polymer compound will be formed, so a raw material polymer substance with a relatively low molecular weight is made into molecules and introduced into the plasma. However, it is difficult to convert raw polymeric substances into molecules without decomposing them. Low-molecular organic compounds are normally gaseous or under reduced pressure,
It can be easily turned into a gas by heating or other methods. However, polymer compounds are solid at normal pressure, and when heated, they are turned into liquid except for some components, but when heated further, a thermal decomposition reaction occurs before evaporation, resulting in lower molecular weight. arise. Normally, a decomposition reaction similarly precedes sputtering or heating using charged particles used in metal vapor deposition.

In the method of the present invention, the decomposition of the raw material polymer is suppressed,
In order to make this into a molecular state, so-called field desorption (F 1e
ld Desorption) method is used. That is, a polymer substance is heated above its softening point or melting point, a DC voltage is applied across an electrode separated by a space, and the attraction force of the electric field causes the polymer substance to form molecular ions or charged particles. It is pulled out into space.

The field desorption method will be briefly explained below.

A high voltage is applied between a sharp wire coated with a polymeric material, the tip of a razor blade, etc., and a counter electrode.
By creating a strong electric field of about 10'V/cm or higher and gradually increasing the temperature, the material applied to the tip becomes partially ionized and ejects. In this case, the material forms very fine droplets,
Sometimes it comes out in the form of a jet, and sometimes it comes out in the form of molecules, so-called molecular ions. In mass spectrometry, the latter phenomenon is applied as an ionization method to measure molecular ion spectra of refractory substances, but since mass spectra can be obtained with very small amounts of ions, jet injection is not used. Rather, they are considered harmful and are removed by pretreatment.

In the method of the present invention, both jet Y jets and molecular ions are effectively utilized. Minimizes the decomposition of difficult-to-volatile substances such as polymeric substances, converts them into molecules, and extracts them into the gas phase. It is then introduced either directly onto the substrate to be coated or into a low temperature plasma. The energy level of the plasma is controlled by gas pressure, frequency, and supplied power so that radical excitation occurs but molecular decomposition is unlikely to occur.

The introduced raw material polymer substance is excited by the plasma and is further polymerized and deposited on the substrate, or polymerized after being deposited on the substrate to obtain an organic thin film having strong adhesion to the substrate. Before introducing the raw material, it is possible to etch the substrate surface with plasma or form an intermediate bonding layer, thereby further improving the adhesion between the substrate and the polymer thin film.

The molecular structure of the thin film produced by the method of the present invention is close to that of polymers obtained by ordinary polymerization reactions.

The thin film material used in the method of the invention may be any heat-melting (relatively low molecular weight) polymer, but for example (polystyrene, polyethylene glycol) are particularly preferred.

The second gist of the present invention is ('I) having an electrode that can heat an organic substance, which is a raw material for forming a thin film, to a temperature equal to or higher than its softening point, and that holds the raw material and an electrode that faces across a space; comprising a raw material supply device that generates an electric field when a voltage is applied between the electrodes and desorbs the raw organic substance in molecular form from the holding electrode; and an electrode that generates (TI) glow discharge plasma. An apparatus for forming an organic thin film on a substrate.

Preferred embodiments of the apparatus of the present invention are shown in FIGS. 1-3.

Hereinafter, the method and apparatus of the present invention will be specifically described with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 is a diagram showing an example of the schematic configuration of the entire apparatus of the present invention, and FIGS. 2 and 3 are diagrams showing examples of the schematic configuration of the electric field desorption device of the apparatus of the present invention.

In FIG. 1, a substrate 2 to be coated is placed on an electrode 3 for high-frequency glow discharge. The electrode 3 has a heating heater (or a cooling device if necessary) 4, and can heat or cool the substrate 2. There is a high-frequency glow discharge type pole 1 facing the electrode 3, and plasma is generated by applying a high voltage from a high-frequency power source 6 to these electrodes.

The polymer substance is supplied in molecular form from the field desorption device 5 into the plasma and deposited on the substrate 2. There is a gas inlet lower and a gas outlet 8, and it is possible to bring the air inside the device under an inert gas atmosphere and to change and adjust the gas phase composition.

In FIG. 2, the field desorption device 5 of the - embodiment includes an emitter 10 (for example, tungsten/silicon), an emitter holder 11, a charged particle focusing system 12, and an emitter case 13. Unlike an emitter for mass spectrometry, the emitter 10 needs to be supplied with a polymer material necessary for coating, so it has a spiral shape as a whole, and has a structure that can be moved and rotated (in the direction of the arrow) in order to efficiently utilize the whole. It has become. The emitter 10 is connected to an emitter power source (not shown) and is further connected to a high voltage power source 14. A raw polymer material is applied to the emitter 10.

In FIG. 3, a separate electric field desorption device 5 has a charged particle focusing system 19, a high voltage power source 20, a heater 15, and a plunger 16. The raw material polymeric substance 17 is continuously supplied from the tip 18 while being extruded by the plunger 16 (in the direction of the arrow).

In the apparatus, the electrode for volatilizing the raw material polymer substance can be selected as appropriate, but it is preferably a tungsten wire or one on which silicone or carbon whiskers are grown. An electric current is passed through the electrode to heat it, raising the temperature to the softening or melting temperature of the polymeric substance.

The shape of the emitter, the number of field desorption devices, their positional relationship with the glow discharge chamber, the structure of the glow discharge chamber, etc. can be designed to be appropriate for the shape of the substrate, etc.

[Effect of the Invention 1] The organic thin film forming method and apparatus of the present invention can form a dense thin film with far superior adhesion to a substrate compared to conventional methods without impairing the physical properties of the raw material polymer.

[Example] EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 Polystyrene was dissolved in toluene, applied to an emitter, and after drying, the emitter was attached to a field desorption device. Glow discharge was ignited in an argon atmosphere at a pressure of 0.1 Torr, and the nickel substrate placed on the electrode-L was held in the argon plasma for 10 minutes, while applying a voltage of about 10 KV between the emitter and the extraction electrode. The emitter current was gradually increased. With the introduction of polystyrene,
After confirming that the light emission state of the glow discharge changed, the substrate was coated for about 30 minutes. As a result, the thickness is about l
An organic thin film of rlO0 was obtained.

This organic thin film showed much better adhesion than a thin film obtained by applying and drying a polystyrene solution. In addition, the thin film obtained by introducing styrene monomer gas into the plasma has poor flexibility;
This organic thin film was flexible, whereas it exhibited brittle properties.

Example 2 A polyimide resin was dissolved in N-methyl-2-pyrrolidone, applied to an emitter, and after the solvent was evaporated, the emitter was attached to an electric field desorption device.

Emitter current and extraction voltage were adjusted in the same manner as in Example 1, and a polyimide resin thin film was formed on a nickel substrate. This thin film showed better adhesion than a polyimide thin film made by diluting it in a solvent, coating it, and drying it.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the schematic configuration of the entire apparatus of the present invention, and FIGS. 2 and 3 are diagrams showing examples of the schematic configuration of the electric field desorption device of the apparatus of the present invention. , 3... Electrode, 2... Substrate, 4... Heater, 5
...Electric field desorption device, 6...High frequency power source, 7...Gas inlet, 8...Gas outlet, 10...Emitter, 1
1... Emitter holder, 12.19... Charged particle focusing system, 1=11- 3... Emitter case, 14.20... High voltage power supply, 15... Heater, 16... Plunger , 17
... Raw material polymeric substance, 18... Tip part. Patent Applicant Sumitomo Electric Industries Co., Ltd. Representative Patent Attorney 2 Idiots - 12= ~O-r Procedural Amendment (Voluntary) March 29, 1985 Patent Application No. 143899 of 1988 2 Invention Name Organic thin film forming method and apparatus 3, relationship with the amended person case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka-shi, Osaka Name (2)
13) Sumitomo Electric Industries, Ltd. 4, Agent 7, first amended the following points in the statement of contents of the amendment. ■As per the appendix in the claims section. ■6 Detailed description of the invention column (1), line 7 at the end of page 4, after ``melting,'' it says ``A high voltage is applied between the counter electrode and the organic material is melted using the attractive force of the electric field. Insert ``. (2) Delete "DC" in line 5 at the end of page 5. I-L (Attachment) Claims (1) Melting an organic substance that is a raw material for forming a thin film,
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-! dan-1, ヱ;, -□η The pM force is made into the form of a 41i-river-rep horizontal substance-sword molecule and introduced into the plasma together with other source materials as desired, and the source materials and other materials as desired are introduced into the plasma. 1. A method for forming an organic thin film, which comprises forming an organic thin film containing a raw material on a substrate-1-. (2) It has an electrode that can heat the organic material that is the raw material for thin film formation to a temperature that will soften it, and has an electrode that holds the raw material and an electrode that faces each other across a space, and a voltage is applied between the electrodes. When an electric field is applied, an electric field is generated, and (II) a glow discharge. An apparatus for forming an organic thin film on a substrate-1-, comprising an electrode for generating plasma.

Claims (2)

[Claims] (1) An organic substance that is a raw material for forming a thin film is melted, made into molecules, and introduced into a plasma together with other raw materials if desired, and an organic thin film containing the raw material and other raw materials if desired is formed on a substrate. 1. A method for forming an organic thin film, characterized by forming the organic thin film. (2) (I) It is possible to heat the organic substance that is the raw material for thin film formation to a temperature above its softening point, and it has an electrode that holds the raw material and an electrode that faces across a space, and a voltage is applied between the electrodes. (ii) forming an organic thin film on a substrate, comprising: a raw material supply device that generates an electric field and detaches the raw organic material in molecular form from the holding electrode when device to do.